Geometrical instrument.



A. E. ANDERSON. GEOMETRICALINSTRUMENT. APPLICATION FILED DEC. 26. 19.16.

15,260,292; Patented Mar. 26, 191s.

mmsQ/y INI/ENTOR- A TT ORNEYS.'

ANDREW ELLIOTT ANDERSON, OF BROWNSVILLE, TEXAS.

n GEOMETRICAL INSTRUMENT.

Specification of Letters Patent.

Patented Mar. 26, i918.

Application iiled December 26, 1916. Serial No. 138,812.

To all lwhom t may concern.'

Be it known that l, ANDREW ELLIOTT ANDERSON, a eitizenfof the United States of America, residing at Brownsville, in the county of Cameron and State of Texas, have invented new and useful improvements in Geometrical instruments, of which the following is a specification.

The present invention relates to improvements in geometrical instruments of the straight-edge type and involves the use of pivoted blades, as in a protractor, for lay-v ing` out, measuring or protracting angles, etc.

The invention is designed to provide an instrument of this character having straight edges movable in the same plane and in such a manner that any angle between Zero and 1800 may be laid out, and either of which straight edges may be made free and unobstructed from end to end in order that the drawing of a line from Aend to end of the straight edge is made possible, and also in order that the measuring or` scaling of a line by`v any suitable means found desirable is facilitated.

The invention consistsr in certain novel combinations and arrangements of parts as will be hereinafter described and claimed.

Figure 1 is a top plan view of my complete instrument.

Fig. 2 is a plan view of one of the blades detached. v

Fig. 3 is a view'in elevation showing one blade in position, the base ring being broken away and the second blade omitted for convenience of illustration.

Fig. 4l is a detail plan view of a vernier plate.

Fig. 5 is a detail plan view of a clamp plate.

Fig- 6 is a sectional view, enlarged, on line tra Fig. l, the section line also being indicated in the same manner in Figs.Y 2, 4i, and 5.

In the'preferred embodiment of my invention as illustrated in my drawings the instrument includes a pair of blades as 1 and 2, of metal or other suitable material, and as arranged and combined with the other elements of the instrument each blade is fashioned with a pair of parallel straight edges, the inner edges of the blades being indicated by the respective numerals 3 and 4: and the outer edges of the blades being indicated by the numerals 5 and 6. The

blades 1 and 2 are movable in the same plane and adapted to swing about the same center, with the inner ends of the inner straight edges always in contact as at the point or corner 7 in Fig. l, and the movement of the blades permits them to be turned or swung from a point of coincidence with the two edges. 3 and a in parallelism and in contact, to measure or lay out between them any angles up to an angle of 1800,

The two blades are combined with the base ring 8 which is a graduated, circular, open center plate, preferably of metal, and the two blades may be swung or revolved about the ring and held in adjusted position by means of a set of plates 9 and 10 and 9 and 10 respectively. The base plates 9 and 9 are each provided with a circular groove 12 coincident with the base ring 8, and as the base plates are provided with a vernier, as shown I will hereinafter call t ein the vernier plates or grooved Vernier plates to distinguish them from their complementary plates of resilient metal 1.0 and 10 which are the clamp plates for holding the blades in adjusted position. The vernier plates and the clamp plates are secured rto the blades by means of screws 11 passing through both plates and the respective blades, and each pair of plates is provided with a fixed screw bar as 13 and 13 Xed in the respective blades and passing through openings or perforations in the pairs of plates. Each of the screw bars has a clamp nut as 14,14 threaded thereon and the nuts bear upon the upper face of the clamp plates, so that by properly turning these 'nuts 1t will readily be seen that t-he ring 3 may be clamped or clasped and held between the pairs of plates, thus rigidly holding the blades with relation to the base ring 8. Each of the clamp plates 10 and 10 is fashioned with a notch or recess as 15 and 15 and these notches are adapted to engage the respective pins 16 and 16 in order to limit the movement of the blades on the base ring. l hen. the two inner ruling edges are fitted together it will be seen that the pins will loe engaged in the notches and in this position the verniers on the plates 9 and 9 are automatically set at zero or rst graduations from the ends of the base ring, the clamp plates being cut away in order that the verniers on the plates and the scale on the ring may be read with facility.

It will readily be seen that both blades ma be swunr about a ooint in the naXis of the base ring to adjusted positiomand the-1 operator may secure an open and unobstructed inner rullng'edge S--by setting'tlre Vernier plate 9 with the vernier at O and turning' the required angle at Vernier off 'Y plate 9. Or an open and unobstructedrulwith each other, With the point 7 always aV Contact point between the blades; and the presence of the break or space between the ends ot the base ring provides for a oo ntinuous ruling'edge 3cr e as desired. The outer ruling edges, when used in connection with the usual parallel ruler, are specially adapted for the platting ot' maps or mapping of iield notes by bearings or azimuths. 1

lVhat-l claim is l. In a geometrical instrument, the combination with a graduated ring7l of a pair of blades movable With respect to said -ring land a Vernier scale carried by each blade, said blades having rulingredges adapted to be disposed at dit'er'ent angles to each other,

the two. plates always contacting at a point in alinemen'tivith said ruling edges and coincident with the center of the ring.

2. An instrument comprising a'graduated base ring7 a1 pair ot blades movable with respect to saidring, a grooved vernier plateV on each ring adapted to receive the ring into the groove thereof andto cooperate with the v graduations'-thereon, and a clamp plate secured to each Vernier plate for locking the parts in adjusted positions.

3. An instrument comprising Va graduated base ring, a blademovableivith respect to said ring and having a groovedplate fixed thereon adapted to receive the ring into the groove vthereof' and to coperate With the gradu-ations thereon,`a clamp plate securedV to the grooved plate and blade, andmeans for clamping the plate and ring in' adjusted positions; f

l. The combination with a blade having a grooved'vernierplate and a resilient clamp plate fixedv thereon7 of a'base ring provided:

with graduations andlooated between said plates, a screiv bar i'Xedto the blade and passed througl'i-the plates,`and`a`nut on the bar for `clamping the plates to the ring; said blade' being movable with respect to said rmg.- Y Y .l

f In testimony whereof my signature.

ANDREWELLIOTT ANDERSON.

Copies ofl this patent may be obtained for ve cents each, by addressing the Commissioner'ofPteiit.

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